new Hard Drive recommendation

thanks, i think the price difference is £1.15p not much! but, they don't have it in stock for 1-2 weeks.

i'm starting to get confused about caching again. if the buffer gets full and it writes to the HDD instead, what happens next does it put it back into memory then write it back to the drive? that's ridiculous. no one ever said what happens. what happens when the cache is full? does anyone know?

 

I'm not sure how the drive cache would prioritize data ON HOLD for reading versus data ON HOLD for writing.

Just dealing with one at a time:

For write buffering, the data moves directly from the cache to the hard drive once either 1) the buffer gets full, whereupon the data is written to the drive on a first-in/first-out basis (FIFO), or 2) All other operations slow down enough that it would impose no additional bottleneck to go ahead and write to the drive.

For read buffering, the data remains in the buffer until either 1) more recent data is available and needs to be buffered for reading or, 2) enough time has passed that the data has certainly become stale.

The cache is basically a "middle man" that holds up data moving in one direction or the other so that the thin "pipeline" moving data back and forth between the hard drive and the CPU/RAM can keep gushing full blast without data or requests for data "backing up" at the entrance to the pipeline.

Another picture for you would be a rubber hose with just the right kind of "weak" spot in it. If there was enough resistance to the water flowing out the end of the hose, the pressure would build up. Eventually, the pressure would get high enough that the weak spot (if elastic enough) would balloon outward, slowing down the pressure buildup rate and providing a reservoir for the excess water flow. For whatever reason, say the water flow eventually slows down (at the inlet to the hose) or the pressure at the end goes down enough that the "weak spot" reservoir now shrinks back down, "flushing" its contents back down the pipeline.

Hope that was helpful.

 

yeap, thanks. i suppose you only need to fully understand it if you're a programmer or a really strange hacker